Impulse traveling in myelinated axon

The movie shows, in the lower panel, an action potential (AP) traveling from left to right in a length (1 cm) of normally-myelinated nerve (10um diam, 150 myelin wraps). Ten nodes are spaced 1000um (1 mm) apart and are numbered from left to right. In the upper panel, two recording electrodes, located at nodes 1 (red) and 9 (black), record the AP as a function of time.

Although impulse propagation in a myelinated axon is said to be "saltatory" ("jumping" from node to node), one can see in the spatial voltage profile that the AP involves many nodes simultaneously. The location of the nodes (where strong ionic currents flow) can be detected by the sharp cusps in the waveform on its rising phase and dips on its falling phase.